Hanstein Stefan M, Felle Hubert H
Botanisches Institut I, Justus-Liebig-Universität, D-35390 Giessen, Germany.
Plant Physiol. 2002 Oct;130(2):940-50. doi: 10.1104/pp.004283.
The influence of CO(2) on Cl(-) release from guard cells was investigated within the intact leaf by monitoring the Cl(-) activity in the apoplastic fluid of guard cells with a Cl(-)-sensitive microelectrode. In illuminated leaves adapted to a CO(2) concentration within the cuvette of 350 microL L(-1), an increase of 250 microL L(-1) CO(2) triggered a transient rise in the apoplastic Cl(-) activity from 3 to 14 mM within 10 min. This Cl(-) response was similar to the Cl(-) efflux evoked by turning off the light, when the substomatal CO(2) was kept constant (CO(2) clamp). Without CO(2) clamp, substomatal CO(2) increased by 120 microL L(-1) upon "light off." The response to an increase in CO(2) within the cuvette from 250 to 500 microL L(-1) in dark-adapted leaves was equivalent to the response to an increase from 350 to 600 microL L(-1) in the light. No Cl(-) efflux was triggered by 2-min CO(2) pulses (150-800 microL L(-1)). After a switch from 350 microL L(-1) to CO(2)-free cuvette air, the guard cells were less sensitive to a rise in CO(2) and to light off, but the sensitivity to both stimuli partially recovered. Changes in CO(2) also caused changes of the guard cell apoplastic voltage, which were generally faster than the observed Cl(-) responses, and which also promptly occurred when CO(2) did not initiate Cl(-) efflux. The comparatively slow activation of Cl(-) efflux by CO(2) indicates that an intermediate effector derived from CO(2) has to accumulate to fully activate plasma membrane anion channels of guard cells.
通过使用对Cl⁻敏感的微电极监测保卫细胞质外体流体中的Cl⁻活性，在完整叶片内研究了CO₂对保卫细胞释放Cl⁻的影响。在适应比色皿中350 μL L⁻¹的CO₂浓度的光照叶片中，将CO₂浓度增加250 μL L⁻¹会在10分钟内使质外体Cl⁻活性从3 mM瞬时升至14 mM。这种Cl⁻反应类似于在气孔下CO₂保持恒定（CO₂钳制）时关灯诱发的Cl⁻外流。没有CO₂钳制时，“关灯”后气孔下CO₂增加120 μL L⁻¹。在暗适应叶片中，比色皿中CO₂从250 μL L⁻¹增加到500 μL L⁻¹的反应与光照下从350 μL L⁻¹增加到600 μL L⁻¹的反应相当。2分钟的CO₂脉冲（150 - 800 μL L⁻¹）不会触发Cl⁻外流。从350 μL L⁻¹切换到无CO₂的比色皿空气后，保卫细胞对CO₂升高和关灯的敏感性降低，但对两种刺激的敏感性部分恢复。CO₂的变化也会导致保卫细胞质外体电压的变化，这种变化通常比观察到的Cl⁻反应更快，并且在CO₂不引发Cl⁻外流时也会迅速发生。CO₂对Cl⁻外流的激活相对较慢，这表明源自CO₂的中间效应物必须积累才能完全激活保卫细胞质膜阴离子通道。
